Probably the most common method of irrigating landscape areas of vegetation is by the use of sprinklers. In a typical irrigation system various types of sprinklers are used to distribute water over a desired area. In general, sprinkler devices are divided into two types, namely rotating stream type and fixed spray pattern type. The stream type sprinkler, commonly referred to as a rotor, trajects a stream of water outwardly from a nozzle, which is rotating slowly over a predetermined arc or complete circle. The spray type sprinkler sprays water from a stationary nozzle, the pattern of coverage being determined by the geometric shape of the discharge passage of the nozzle.
For reasons well known to those involved in the design of irrigation systems, the precipitation rate of the rotor type sprinklers is much lower than the precipitation rate of the fixed nozzle type sprinkler. For proper irrigation of plant life and conservation of water it is extremely important to have a uniform or prescribed amount of water delivered by the irrigation system to a specific area. Because of the difference in precipitation rates of the two types of sprinklers, heretofore it has been necessary to operate the rotor type of sprinkler for a longer time than the spray type sprinkler. In order to accomplish this, it has been necessary to have the two types of sprinklers operated separately whereby each type could be operated for a suitable time to supply the desired total precipitation to the irrigated area. Prior to this invention many attempts have been made to reduce the precipitation rates of spray type sprinklers. Most, if not all of such attempts have been concentrated on the design of the nozzles in order to reduce the rate of flow of water.